関係代名詞の使い方, part 7: comma or no comma?

Yesterday I left you with this question: how can you turn these two sentences into one sentence using "where"? Here's the answer:

• I was teaching in a building at this intersection. The Nihonbashi Mitsukoshi department store is also located at this intersection.
• I was teaching in a building at this intersection, where Nihonbashi Mitsukoshi department store is also located.

Now, think about these sentences. Identify the relative clauses. Some of them use commas, and some of them don't. Why?

I'm going to enjoy some extra free time next week, which is a holiday.
The holiday, which is a Buddhist one, honors the spirits of our ancestors. (see Wikipedia:
http://en.wikipedia.org/wiki/Bon_festival )

• 敬う (うやまう) (v5u,vt) to show respect; to honour; to honor; (P); <- is this right?
• 先祖 (せんぞ) (n,adj-no) ancestor; (P); <- how about this one?

There's no holiday which is similar in America, I think.
America has holidays which are religious and holidays which are political, but nothing like O-Bon, I think.
I'm going to play the drum which I posted a picture of a few days ago.

The picture which I have posted today is of my ancestors. The pictures were gathered by my uncle, who lives in Georgia now. <- no comma, and then a comma... why?

More tomorrow!